Well, the problem is that under Layer 7 list of available applications you can choose from does not have required programs (in my case Skype and ooVoo). Is there any way to add those applications manually by yourself?

Unfortunately neither "skypeout" nor "skypetoskype" is working to prevent the Skype application from running. I'm just wondering if anyone is aware of how to add applications to the Restriction List (Layer 7).

Skype must "call home" - I'd capture a tcpdump trace of the initial connection and then block all connections to that destination IP (or IPs - I'm assuming it's using a DNS record which may/probably do map do multiple destination IPs, but you can always block the entire subnet if applicable).